DE2348624A1 - HYDRAULIC AMPLIFIER, IN PARTICULAR BRAKE AMPLIFIER - Google Patents

Description

Dr. Ing.H. Negendar * Dip «. Ing. H. Heuck - Dipl. Pnys. W. Schmitt DIpI. Ing.E. Graaffs - Dip *. Ing. W. Wehrwrrt

• IübcImii 2, Mozaitstrasse · 2S

T-phone 5380586

The Bendix Corporation

Executive offices

Bendix Center September 26, 1973

Southfield, Mich. 43O75, U.S. Attorney File M-2802

Hydraulic booster, in particular brake booster

The invention relates to a hydraulic booster which can be used, for example, in the braking system of a vehicle.

A disadvantage of most hydraulically operated brake boosters is that the power assistance is lost immediately when the power pump that delivers the pressure medium to the booster steering of the vehicle fails. This disadvantage becomes very critical, for example, when the vehicle is descending a steep incline and the engine of the vehicle "dies", whereby the drive of the pump for the power steering is prevented.

As described in the US-PS 3 638 528, it has already been proposed a hydraulic brake booster with a secondary pressure

409 81.4 / 1OU

source to provide. This consists of a collector who has the Pressure medium generated for power steering when the pump is running normally saves so that it is available in the event of a pump failure. The power assistance is not lost immediately. Devices of the type described in the aforementioned patent are only used in brake boosters of the so-called "parallel" type can be used, a type in which the connection of the pressure medium in the booster pressure chamber controlling valve connected in parallel with the booster piston is.

However, it is already a hydraulic booster for hydraulic Systems on vehicles known, which corresponds to the so-called "concentric" type. Such an amplifier has a housing with a bore extending through the housing, within which a piston is displaceable, and with one end of the housing cooperates to form a pressure chamber opposite this end. A first valve carried by the piston can be displaced in relation to the piston from a first position, which serves to ventilate the pressure chamber, into a second position; the first valve, when moved to the second position, subsequently allows higher pressures from a primary source into the pressure chamber reach to move the piston towards the other end of the bore. The first valve moves together

j with the piston, xv when this is in the direction of the other end

the hole moves.

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j Proceeding from this, the invention is characterized in that the Booster has a second valve carried by the housing, to fluid communication from a secondary pressure source into the pressure chamber to control connecting means to operate over the entire range of sliding movement of the piston the first valve connects to the second valve to actuate the second valve when the first valve is over the second Position is shifted, and that the connecting device enables that the first valve moves relative to the housing when it moves together with the piston.

As a result of this feature, the opening of the "second valve" only depends on the position of the first valve with respect to the piston; the additional or complementary and pressurized fluid can flow into the booster chamber as soon as needed. The arrangement described above provides an auxiliary drive source for the brake booster of the so-called "concentric" type if the pump for the power steering of the vehicle fails should.

The invention is explained below using an exemplary embodiment with reference to the accompanying drawing.

Fig. 1. Figure 3 is a longitudinal sectional view of a "concentric" type booster for the braking system of a vehicle according to the invention; and '.

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Fig. 2 is a sectional view taken from line 2-2 in Fig. 1 at below Simultaneous schematic representation of the pump for the power steering of the vehicle and the power steering gear.

In the drawings, a hydraulic booster 10 is shown}, which has a housing 12 -with a bore 14 located therein. A piston 16 is displaceable within the bore 14, j one end of the piston 16 cooperating with the corresponding end of the bore 14 and forming a pressure chamber 18 therewith. A rod 20 connects the other end of the piston 16 to a conventional automotive main cylinder (not shown), which in FIG. 1 is attached to the left side of the housing 12 and can be actuated by the rod 20 when the piston 16 is laughed shifted to the left.

The outer surface of the piston 16 is diametrically opposed to a first set opposed and axially extending grooves or slots 22,24 with a second set of diametrically opposed ones and axially extending grooves or slots 26, 28 and with a third set of diametrically opposed ones and axially extending grooves or slots 30,32. The grooves or slots 22 and 24 are associated with the outlet and with the High pressure side of the pump 34 for the power steering of the vehicle

j in connection, the grooves 26 and 28 are connected to the inlet of the

Steering gear 36 for the vehicle in connection, while the grooves 30 and 32 with the inlet or low pressure side of the pump 34 |

stay in contact. The outlet of the steering gear 36 is also "4098 U / 10 14 _ ₅ _

with the inlet side of the pump 34 in communication.

The housing 12 is also equipped with a transverse bore 38, which is connected to the groove 24. The transverse bore 38 connects the groove 24 to a collector or a pressure medium reservoir 40. The collector 40 can correspond to known embodiments, such as those shown and described in US Pat. No. 3,282,786 is. A check valve 42 is fixed within the bore 38 and has a valve body 44 which through a spring 48 is pressed against a valve seat 46 with a seal in order to connect the pressure medium from the collector 40 into the groove 24 to prevent, but to allow the connection in the opposite direction. A plunger 50 is also slidable within the bore 38 held and radially movable with respect to the bore 14; the plunger 50 extends into the groove 24. If the plunger 50 in the bore 38 is then pushed At the end of the plunger, the valve body 44 in a direction facing away from the valve seat 46 in order to establish the fluid connection from the collector 40 into the To enable groove 24, as will be explained in detail below. On the circumference of the plunger 50 shoulders are formed around the To enable pressure medium connection along the plunger 50 between the bore 38 and the groove 24. An elongated element or a The rod 52 is arranged within the groove 24 and extends essentially over the entire axial length thereof. If the • The piston is moved - the rod 52 moves accordingly with this. The end of the plunger 50 is slidable on the

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Rod or element 52, so that the rod can move in the axial direction with respect to the plunger. A movement of the rod 52 which is directed radially with respect to the bore 14, however, results in j

to the fact that the plunger 50 is pushed back into the bore 38. j Another plunger 54 extends radially through the wall of the

j piston 16 between a bore formed within piston 16 and groove 24. One end of the plunger 54 is located on the rod 52, so that the rod 52 at the radial movement of the plunger 54 also of the piston 16 is displaced radially with respect to \ to urge the plunger in accordance with the 50th In the same way i flat parts or shoulders are formed on the plunger 54 in order to connect the bore 56 to the groove 24. The tappets or plungers 50 and 54 and the element 52 together form a joint device 58, the ziveck of which is discussed in more detail below.

A valve spindle 60 is held displaceably within the bore 56 and has grooves 62, 64 as well as shoulders or shoulders 66, 67 and 68 are formed. These act with corresponding grooves 70, 72 and with shoulders 74, 76 on the wall of the bore 56 together to control the connection in the direction of the pressure chamber 18. The groove 70 stands with the groove 24 and consequently with it the outlet or high pressure side of the pump 34 in connection. In a comparable manner, the groove 62 with the grooves 26 and 28 and consequently with the inlet of the power steering gear 36 in conjunction manure. i) The groove 72 stands with centers 50 and 32 and consequently with the inlet or the low-pressure side of the pump 34 in connection

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manure. The groove 64 communicates with the pressure chamber 18 via a channel 78 in connection. A cam or control surface 80 is at one end of a groove 81 between shoulders 66 and 67 of the valve stem 60 trained. When the latter is shifted sufficiently, the control surface 80 comes into contact with the edge of the plunger 54, whereby it is displaced radially with respect to the piston 16

t j will. In a corresponding manner, the rod 52 and the other

Plunger 50 moved in the manner explained above.

The valve spindle 60 is displaced by an input rod 82, one end (not shown) of which is connected to the ordinary brake pedal within the driver's compartment. The other The end of the rod rests against the valve spindle 60 in order to move it. A spring 84 presses the valve stem 60 and consequently the input rod 82 according to FIG. 1 to the right, so that stops 86 carried by the input rod 82 to corresponding, stops 88 carried by the piston 16 are applied. In this way, the unloaded position of the valve spindle 60 is determined. The piston 16 and the valve stem carried within the piston 60 are tensioned to the right by the brake return spring 60 as shown in FIG. 1, so that the right end of the Piston 16 is normally applied to the end of the bore 14. This state corresponds to the brake release position of the Piston 16.

The amplifier 10 operates as follows:

S The various components of the brake booster 10 are in ι 4098U / 10U

the FIGS. 1 and 2 reproduced in the position in which they take when releasing the brakes of the vehicle. In this position the groove 70 communicates with the groove 76 so that substantially all of the flow from the pump 34 into the booster Fluid forwarded directly to the power steering gear 36 will. In a comparable way, there is a connection between the pressure chamber 18 and the low-pressure side of the pump 34, the connection being via the channel 78, the grooves 74 and 72 and the slots or grooves 30 and 32. When applying the brake;

or the brakes, the valve spindle 60 according to FIG. 1 to the left displaced so that the shoulder 68 overlaps the shoulder 74 and fluid communication from the pressure chamber 18 in the direction of the Inlet or the low pressure set of the pump 34 ended. Simultaneously the shoulder 67 moves in a direction away from the shoulder 74, around the groove 70 with the groove 64 and consequently to be connected to the pressure chamber 80 via the channel 78. At about the same time, that is between the end of shoulder 66 and the The opening formed at the end of the shoulder 76 is considerably reduced, so that the fluid connection between the groove 70 and the groove 62 is constricted or is limited. As a result, a higher pressure develops within the groove 70, which as mentioned above enters the pressure chamber 18. The pressure within the chamber 18 acts at the right end of the piston 16 and pushes it according to Fig. 1 to the left. Since this movement is transmitted to the aforementioned master cylinder (not shown) by means of the rod 20 the actuation of the piston 16 leads to the application of the brake in the normal manner.

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The in the groove 70 as a result of the constriction of the connection between the groove 70 and the groove 62 developed high pressure also reaches the collector 40, since the transverse bore 38 on the Slot 24 is also connected to the groove 70. The check valve 42, of course, allows fluid communication from the Groove 24 in the collector 40, but prevents the connection in the opposite direction * Fluid under high pressure is even introduced into the collector 40 when the brakes of the vehicle are released, if the power steering gear 36 of the Vehicle is actuated and a counterpressure develops in the hydraulic system. So it becomes a complete at any point in time charged accumulator or pressure accumulator ensured, while the pump 34 for the power steering of the vehicle normally operates.

When the high pressure output of the pump 34 for power steering as a result If there is no malfunction, for example if the engine of the vehicle dies, then the driver shifts when the brake is actuated, the valve spindle 60 moves a small additional distance to the left (FIG. 1). When moving the valve spindle comes the cam or control surface 80 in contact with the end of the plunger 54, so that the plunger 54 along the Control surface 80 slides upward. The plunger 54 is displaced radially outward with respect to the piston 16. These j radial, outward movement of the plunger 54 is transmitted to the plunger 50 via j the element or rod 52, where-

by this the valve body 44 lifts from the valve seat 46 to

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the pressure medium content of the memory or collector 40 via the grooves 70 and 64 and the channel 78 to get into the pressure chamber 18. That coming from the collector 40 into the pressure chamber 18 Pressure of the fluid then normally causes the brakes to be applied by displacing the piston 16 as mentioned above will. When the piston 16 is driven by the accumulator 40 or driven by the primary pressure when the brakes are applied the pump 34 is displaced then the rod 52 can move axially with respect to the plunger on the entire axial movement of the piston 16 15 relocate. However, if at any time during the movement of the piston 16 there is a need for pressure of the fluid in the accumulator 40 exists, then the connection or articulation system 58 is actuated by additional displacement of the valve spindle 60 to to allow the required pressure of the fluid from the collector 40 to reach the pressure chamber 18.

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Claims (9)

Claims 1.! Hydraulic booster with a bore Housing within which a piston is displaceable and with one end of the Bohrimg cooperating with this one therebetween located pressure chamber forms, with one of the piston carried first valve, which from a pressure chamber venting position relative to the piston in a second position is displaceable and which "in the sequence from a primary pressure source higher pressures can get into the pressure chamber when it moves in the direction of the second position to the To move the piston in the direction of the other end of the bore, the first valve being movable together with the piston, when this slides in the direction of the other end of the bore, characterized in that the amplifier passes through the housing (12) carried second valve (42) to the Fluid connection from a secondary pressure source into the 40981 01 A 1 kl -12- Pressure chamber (18) to control that a connecting device (58) for the entire range of sliding movement of the piston (16), the first valve (60) is operative with the second valve (42) connects to operate the second valve when the first valve is displaced beyond the second position and that the connecting means enables the first valve displaced relative to the housing (12) when it moves together with the piston. 2. Hydraulic booster according to claim 1, characterized in that that the housing (12) has an inlet opening connected to the first pressure medium source (34) and an outlet opening j has that the first valve (60) the fluid connection between j see the inlet port, the outlet port and the pressure chamber (18) control that the piston (16) first, axially I extending slots (22,24), which the inlet opening on the entire range of axial movement of the piston connect to the first valve that second, axially extending slots (26-32) of the piston over the entire area axial piston movement connect the outlet opening to the first valve, and that the connecting device (58) extends through one (24) of the slots. 3. Hydraulic booster according to one of claims 1 and 2, characterized in that the link means (58) comprises a first plunger (54) which -13-409814 / 1014 supported by the piston (16) and movable as the first valve (60) moves past the second position, further a second plunger (50) which is movable to open the second valve (42), and a member (52) which the Plunger connects to transmit the movement of the first plunger to the second plunger, and that the element (52) parallel to the axis of the bore (14) allows a relative movement of the first plunger with respect to the second plunger. 4. Hydraulic booster according to claim 3, characterized that the first plunger (54) extends through the wall of the piston (16) in a substantially radially directed manner, that the first Valve (60) has means (80) for displacing the plunger in a substantially radial direction when the first valve is moved moved over the second position, that the second plunger (50) is substantially radially movable to the second Open valve (42); and that the element '(52) is an axial movement allows the first plunger with respect to the second plunger, but transmits a radial movement of the first plunger, in order to displace the second plunger in a substantially radial direction. 5. Hydraulic booster according to one of claims 3 or 4, characterized in that the element (52) is carried by the piston (16) and is movable therewith. -14-4098U / 101 A 6. Hydraulic booster according to claim 2 or 5, characterized in that that the element (52) is held in one (24) of the slots, and that the second pressure medium source (40) is fluid enters the first slots (22,24) when the second valve (42) is open. 7. Hydraulic booster according to one of claims 1 to 6, characterized in that the secondary pressure medium source consists of a device (40) which stores fluid under pressure. 8. Hydraulic booster according to claim 7, for the braking system of a motor vehicle, characterized in that the pressure medium source is a pump (34) driven by the engine of the vehicle and that stores the fluid under pressure Device (40) through which the pressure medium output of the pump is loaded when it is working normally. 9. Hydraulic booster according to claim 8, characterized in that that the high-pressure outlet of the pump (34) is connected to the pressure medium accumulator (40) in order to prevent this at normal To load the barrel of the pump with pressure medium, and that a device (44,46,48) the fluid connection from the outlet of the pumps allows in the pressure medium accumulator, but prevents the connection in the opposite direction. 4098 14/1014